1. Field of the Invention
The present invention relates to a sequential pattern extracting apparatus, a sequential pattern extracting method, and a sequential pattern extracting program in which frequently-appearing sequential data are extracted as a sequential pattern from a data set including sequential data.
2. Description of the Related Art
In a pattern extracting apparatus, when a minimum support specified in advance is made high, only a self-evident pattern is extracted. On the other hand, when the minimum support is made low, extraction processing time is made longer, and a highly frequently-appearing pattern is extracted regardless of the existence or nonexistence of a request from an analyst (user). Thus, a large quantity of extraction results are output in many cases, which makes analysis complicated. This characteristic is made more remarkable as a data volume to be handled increases.
As a measure to solve this problem, there is disclosed in Jpn. Pat. Appln. KOKAI No. 9-251467 that a processing time is shortened by carrying out pattern extraction by using only appropriate data items in consideration of the duplication and the worth of data items.
Further, there is disclosed in the following Jpn. Pat. Appln. KOKAI No. 2004-110327 that a processing time is shortened by carrying out refinement of processing object data and suppression of extracted results based on a constraint specified in advance, and only an extracted pattern necessary for an analyst is output.
In the method disclosed in the above-described Jpn. Pat. Appln. KOKAI No. 9-251467, since a useful pattern is extracted in some cases by using items determined to be improper, there is a problem that omission in an extracted result is brought about. Further, in the method disclosed in the above-described Jpn. Pat. Appln. KOKAI No. 2004-110327, the constraint specified in advance does not contribute to the efficiency of the pattern extraction processing itself, and there is a problem that a tremendous extraction processing time is required when processing object data as a result of refinement based on the constraint is enormous.
Accordingly, in a conventional sequential pattern extracting apparatus, even a useful sequential pattern is not extracted in some cases. Or, there is a problem that extraction processing time is long.